Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Further, the wind turbine may include various bearings to facilitate rotation of its various components. Two examples of such bearings include pitch bearings and yaw bearings. More specifically, yaw bearings are configured to rotate the nacelle with respect to the tower as a function of the incoming wind. In addition, pitch bearings are arranged between a blade root of the rotor blades and the hub. Therefore, the pitch bearings rotate or pitch the rotor blades with respect to the incoming wind.
Such bearings generally include an outer race, an inner race rotatable relative to the outer race, and a plurality of rolling elements therebetween. Many wind turbine bearings include point contact rolling elements, e.g. ball bearings 1, such as those illustrated in FIG. 1. Alternatively, as shown in FIG. 2, some wind turbine bearings may include line contact rolling elements, such as cylindrical rolling elements 2, having a 0° and 90° contact angle configuration.
Conventional line contact rolling elements typically include the rolling elements arranged in a 0° and 90° contact angle configuration. More specifically, as shown in FIG. 3, a partial, cross-sectional view of a line contact rolling element bearing 3 according to conventional construction is illustrated. As shown, the line contact rolling element bearing 3 includes an outer race 7 and an inner race 8 rotatable relative to the outer race 7 via a plurality of line contact rolling elements 4, 5, 6. More specifically, as shown, the upper and lower line contact rolling elements 4, 5 have a 90° contact angle, whereas the middle line contact rolling element 6 has a 0° contact angle.
In such configurations, the rolling elements having a 90° contact angle experience relative sliding therebetween as well as with raceway in order to function. Successful utilization of line contact rolling elements in a 90° contact angle configuration typically relies on operation in lubrication lambda regimes greater than one such that the relative sliding is not detrimental to bearing performance. However, wind turbine pitch bearings experience lambda ratios approaching zero. Thus, when line contact rolling element bearings are used as pitch bearings, such sliding can scuff and wear interface surfaces, generating heat and debris inside the bearing.
Accordingly, a pitch bearing having line contact rolling elements that addresses the aforementioned issues would be welcomed in the technology. In particular, a pitch bearing with less than three rows of line contact rolling elements would be beneficial.